/**
 * @file
 *
 * @defgroup zepif ZEP - ZigBee Encapsulation Protocol
 * @ingroup netifs
 * A netif implementing the ZigBee Encapsulation Protocol (ZEP).
 * This is used to tunnel 6LowPAN over UDP.
 *
 * Usage (there must be a default netif before!):
 * @code{.c}
 *   netif_add(&zep_netif, NULL, NULL, NULL, NULL, zepif_init, tcpip_6lowpan_input);
 *   netif_create_ip6_linklocal_address(&zep_netif, 1);
 *   netif_set_up(&zep_netif);
 *   netif_set_link_up(&zep_netif);
 * @endcode
 */

/*
 * Copyright (c) 2018 Simon Goldschmidt
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Simon Goldschmidt <goldsimon@gmx.de>
 *
 */

#include "netif/zepif.h"

#if LWIP_IPV6 && LWIP_UDP

#include "netif/lowpan6.h"
#include "lwip/udp.h"
#include "lwip/timeouts.h"
#include <string.h>

/** Define this to 1 to loop back TX packets for testing */
#ifndef ZEPIF_LOOPBACK
#define ZEPIF_LOOPBACK 0
#endif

#define ZEP_MAX_DATA_LEN 127

#ifdef PACK_STRUCT_USE_INCLUDES
#include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct zep_hdr {
    PACK_STRUCT_FLD_8(u8_t prot_id[2]);
    PACK_STRUCT_FLD_8(u8_t prot_version);
    PACK_STRUCT_FLD_8(u8_t type);
    PACK_STRUCT_FLD_8(u8_t channel_id);
    PACK_STRUCT_FIELD(u16_t device_id);
    PACK_STRUCT_FLD_8(u8_t crc_mode);
    PACK_STRUCT_FLD_8(u8_t unknown_1);
    PACK_STRUCT_FIELD(u32_t timestamp[2]);
    PACK_STRUCT_FIELD(u32_t seq_num);
    PACK_STRUCT_FLD_8(u8_t unknown_2[10]);
    PACK_STRUCT_FLD_8(u8_t len);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#include "arch/epstruct.h"
#endif

struct zepif_state {
    struct zepif_init init;
    struct udp_pcb *pcb;
    u32_t seqno;
};

static u8_t zep_lowpan_timer_running;

/* Helper function that calls the 6LoWPAN timer and reschedules itself */
static void zep_lowpan_timer(void *arg)
{
    lowpan6_tmr();

    if (zep_lowpan_timer_running) {
        sys_timeout(LOWPAN6_TMR_INTERVAL, zep_lowpan_timer, arg);
    }
}

/* Pass received pbufs into 6LowPAN netif */
static void zepif_udp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p,
                           const ip_addr_t *addr, u16_t port)
{
    err_t err;
    struct netif *netif_lowpan6 = (struct netif *)arg;
    struct zep_hdr *zep;

    LWIP_ASSERT("arg != NULL", arg != NULL);
    LWIP_ASSERT("pcb != NULL", pcb != NULL);
    LWIP_UNUSED_ARG(pcb); /* for LWIP_NOASSERT */
    LWIP_UNUSED_ARG(addr);
    LWIP_UNUSED_ARG(port);

    if (p == NULL) {
        return;
    }

    /* Parse and hide the ZEP header */
    if (p->len < sizeof(struct zep_hdr)) {
        /* need the zep_hdr in one piece */
        goto err_return;
    }

    zep = (struct zep_hdr *)p->payload;

    if (zep->prot_id[0] != 'E') {
        goto err_return;
    }

    if (zep->prot_id[1] != 'X') {
        goto err_return;
    }

    if (zep->prot_version != 2) {
        /* we only support this version for now */
        goto err_return;
    }

    if (zep->type != 1) {
        goto err_return;
    }

    if (zep->crc_mode != 1) {
        goto err_return;
    }

    if (zep->len != p->tot_len - sizeof(struct zep_hdr)) {
        goto err_return;
    }

    /* everything seems to be OK, hide the ZEP header */
    if (pbuf_remove_header(p, sizeof(struct zep_hdr))) {
        goto err_return;
    }

    /* TODO Check CRC? */
    /* remove CRC trailer */
    pbuf_realloc(p, p->tot_len - 2);

    /* Call into 6LoWPAN code. */
    err = netif_lowpan6->input(p, netif_lowpan6);

    if (err == ERR_OK) {
        return;
    }

err_return:
    pbuf_free(p);
}

/* Send 6LoWPAN TX packets as UDP broadcast */
static err_t zepif_linkoutput(struct netif *netif, struct pbuf *p)
{
    err_t err;
    struct pbuf *q;
    struct zep_hdr *zep;
    struct zepif_state *state;

    LWIP_ASSERT("invalid netif", netif != NULL);
    LWIP_ASSERT("invalid pbuf", p != NULL);

    if (p->tot_len > ZEP_MAX_DATA_LEN) {
        return ERR_VAL;
    }

    LWIP_ASSERT("TODO: support chained pbufs", p->next == NULL);

    state = (struct zepif_state *)netif->state;
    LWIP_ASSERT("state->pcb != NULL", state->pcb != NULL);

    q = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct zep_hdr) + p->tot_len, PBUF_RAM);

    if (q == NULL) {
        return ERR_MEM;
    }

    zep = (struct zep_hdr *)q->payload;
    memset(zep, 0, sizeof(struct zep_hdr));
    zep->prot_id[0] = 'E';
    zep->prot_id[1] = 'X';
    zep->prot_version = 2;
    zep->type = 1;                  /* Data */
    zep->channel_id = 0;            /* whatever */
    zep->device_id = lwip_htons(1); /* whatever */
    zep->crc_mode = 1;
    zep->unknown_1 = 0xff;
    zep->seq_num = lwip_htonl(state->seqno);
    state->seqno++;
    zep->len = (u8_t)p->tot_len;

    err = pbuf_take_at(q, p->payload, p->tot_len, sizeof(struct zep_hdr));

    if (err == ERR_OK) {
#if ZEPIF_LOOPBACK
        zepif_udp_recv(netif, state->pcb, pbuf_clone(PBUF_RAW, PBUF_RAM, q), NULL, 0);
#endif
        err = udp_sendto(state->pcb, q, state->init.zep_dst_ip_addr, state->init.zep_dst_udp_port);
    }

    pbuf_free(q);

    return err;
}

/**
 * @ingroup zepif
 * Set up a raw 6LowPAN netif and surround it with input- and output
 * functions for ZEP
 */
err_t zepif_init(struct netif *netif)
{
    err_t err;
    struct zepif_init *init_state = (struct zepif_init *)netif->state;
    struct zepif_state *state = (struct zepif_state *)mem_malloc(sizeof(struct zepif_state));

    LWIP_ASSERT("zepif needs an input callback", netif->input != NULL);

    if (state == NULL) {
        return ERR_MEM;
    }

    memset(state, 0, sizeof(struct zepif_state));

    if (init_state != NULL) {
        memcpy(&state->init, init_state, sizeof(struct zepif_init));
    }

    if (state->init.zep_src_udp_port == 0) {
        state->init.zep_src_udp_port = ZEPIF_DEFAULT_UDP_PORT;
    }

    if (state->init.zep_dst_udp_port == 0) {
        state->init.zep_dst_udp_port = ZEPIF_DEFAULT_UDP_PORT;
    }

#if LWIP_IPV4

    if (state->init.zep_dst_ip_addr == NULL) {
        /* With IPv4 enabled, default to broadcasting packets if no address is set */
        state->init.zep_dst_ip_addr = IP_ADDR_BROADCAST;
    }

#endif /* LWIP_IPV4 */

    netif->state = NULL;

    state->pcb = udp_new_ip_type(IPADDR_TYPE_ANY);

    if (state->pcb == NULL) {
        err = ERR_MEM;
        goto err_ret;
    }

    err = udp_bind(state->pcb, state->init.zep_src_ip_addr, state->init.zep_src_udp_port);

    if (err != ERR_OK) {
        goto err_ret;
    }

    if (state->init.zep_netif != NULL) {
        udp_bind_netif(state->pcb, state->init.zep_netif);
    }

    LWIP_ASSERT("udp_bind(lowpan6_broadcast_pcb) failed", err == ERR_OK);
    ip_set_option(state->pcb, SOF_BROADCAST);
    udp_recv(state->pcb, zepif_udp_recv, netif);

    err = lowpan6_if_init(netif);
    LWIP_ASSERT("lowpan6_if_init set a state", netif->state == NULL);

    if (err == ERR_OK) {
        netif->state = state;
        netif->hwaddr_len = 6;

        if (init_state != NULL) {
            memcpy(netif->hwaddr, init_state->addr, 6);
        } else {
            u8_t i;

            for (i = 0; i < 6; i++) {
                netif->hwaddr[i] = i;
            }

            netif->hwaddr[0] &= 0xfc;
        }

        netif->linkoutput = zepif_linkoutput;

        if (!zep_lowpan_timer_running) {
            sys_timeout(LOWPAN6_TMR_INTERVAL, zep_lowpan_timer, NULL);
            zep_lowpan_timer_running = 1;
        }

        return ERR_OK;
    }

err_ret:

    if (state->pcb != NULL) {
        udp_remove(state->pcb);
    }

    mem_free(state);
    return err;
}

#endif /* LWIP_IPV6 && LWIP_UDP */
